Vanadia-titania catalysts have been broadly used to decompose environmentally harmful chlorinated organic compounds generated during incineration or combustion of organic waste. A vanadia-titania catalyst is capable of decomposing such chlorinated organic compounds through an oxidation-reduction reaction, emitting a harmless exhaust gas to the environment.
Generally, such vanadia-titania catalyst is prepared by a wet synthetic method such as impregnation and coprecipitation methods. For example, an aqueous vanadium salt solution is impregnated to a molded titania pellet or powder, and the resulting material is dried and calcined. However, the titania used in the existing wet synthetic method is of an anatase form having a low specific surface area and low thermally stability, and the anatase form of the titania converts in part into the rutile form during the high temperature treatment step, which leads to an inactive catalyst. To avoid such problems, there has developed a modified method that involves an elaborated multi-step procedure and requires a number of days to complete.
There has been reported another method for preparing a vanadia-titania aerogel catalyst by drying a vanadia-titania wet gel prepared by a sol-gel method, which is conducted under a supercritical condition of carbon dioxide and dried also under a supercritical condition. However, this method also has difficulties in that it takes several days to age the gel and that the drying process must be conducted under a superitical condition.
Therefore, the present inventors have endeavored to develop an improved method for preparing a vanadia-titania catalyst, which can be used for converting a chlorinated organic compound into environmentally harmless products, and have found a solvothermal method for preparing a particulate form of a vanadia-titania catalyst having a core-shell structure, which effectively converts chlorinated organic compounds.